In recent years, Ethernet (registered trademark) has been used not only for local area networks (LANs) but also in carrier networks, which are an infrastructure technology for supporting packet networks on which transmission target data is transmitted in the form of packets. Ethernet has become used for not only data communications but also communications that are sensitive to transmission delays and data losses in the middle of transmission, such as synchronous messages, sounds, and moving images. Therefore, it has become desirable to provide monitoring of accurate service of quality (QoS) and the functionality of a high degree of classification of faults.
One of technologies for providing such QoS monitoring and fault classification for Ethernet transmission paths is a set of operation administration and maintenance (OAM) functions defined in Recommendation International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Y.1731 (February 2008). Many functions, such as connectivity monitoring, transmission-path checking, fault notification, and monitoring of transmission delay or a frame loss are included in the set of OAM functions.